(function flexible(window, document) {
  let docEl = document.documentElement;
  let dpr = window.devicePixelRatio || 1;

  function setBodyFontSize() {
    if (document.body) {
      document.body.style.fontSize = (12 * dpr) + 'px';
    } else {
      document.addEventListener('DOMContentLoaded', setBodyFontSize)
    }
  }
  setBodyFontSize();

  function setRemUnit() {
    let rem = Math.min(docEl.clientWidth, 414) / 10;
    docEl.style.fontSize = rem + 'px';
  }

  setRemUnit();

  window.addEventListener('resize', setRemUnit)
  window.addEventListener('pageshow', function (e) {
    if (e.persisted) {
      setRemUnit();
    }
  });

  if (dpr >= 2) {
    let fakeBody = document.createElement('body');
    let testElement = document.createElement('div');
    testElement.style.border = '.5px solid transparent';
    fakeBody.appendChild(testElement);
    docEl.appendChild(fakeBody);
    if (testElement.offsetHeight === 1) {
      docEl.classList.add('hairlines');
    }
    docEl.removeChild(fakeBody);
  }
}(window, document));
